In a continuous high-pressure polyolefin polymerization process, polyethylene product and low-molecular weight waxes are dissolved in the carrier ethylene exiting the reactor. As pressures and temperatures are decreased through various pressure letdown and cooling steps, the product and waxes come out of solution resulting in two distinct phases, one gas and one liquid.
The liquids are subsequently separated from the gas via various separation technologies and equipment. One such device, shown in FIG. 1, includes a vertical cylindrical vessel 10 into which the gas/liquid mixture 11 is fed, a trumpet entry 12 which directs the gas/liquid mixture 11 towards the liquid surface 13 where liquid droplets impinge on and adhere to the liquid surface 13. The separated liquid phase exits the vessel 10 through a liquid outlet 14 located at the bottom of the vessel 10, and the separated gas phase exits the vessel through a gas outlet 15 located at the top of the vessel 10. The separation efficiency of such a device is dependent upon the relative densities and viscosities of the gas and liquid components, droplet sizes, throughputs, and the configuration of the vessel 10 and trumpet 12.
The conventional separation devices are not 100% efficient and some product and waxes pass out of the separation vessels, entrained in the ethylene carrier gas. Entrained liquids increase fouling of downstream heat exchangers resulting in more frequent “burn-outs.” Entrainment of the liquids into compressors and piping where they potentially solidify lowers plant on-stream factors and operating rates, and increases cleaning and maintenance time and costs. In extreme cases, entrained liquids can cause piping blockages and premature failure of mechanical components.
Thus, there is a need in the art for a high-pressure separator with improved separation efficiency to reduce the amount of liquids passing out of the separator with the gas stream and into downstream processes and equipment.